Aw poop! PL400 fried!

NavLinear

NavLinear

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Agree with Lee. It seems that you ordered the wrong part. Here's what we use:

Bergquist - Sil-Pad 400. The part number is SP400-0.009-00-04. The ones you have are 0.007" (with an extra hole) and should be 0.009" in thickness.
 
MarkWComer

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NavLinear said:
Agree with Lee. It seems that you ordered the wrong part. Here's what we use:

Bergquist - Sil-Pad 400. The part number is SP400-0.009-00-04. The ones you have are 0.007" (with an extra hole) and should be 0.009" in thickness.
Click to expand...
I don't know what gives on Mouser's parts numbers. Looking back, I don't think I had a part number for those pads, just a manufacturer and item name. These were the only ones that said "TO-3" in the description, so those were the ones I ordered. The part number you supplied has a picture in the listing but it shows a TO-218 type transistor.
 
MarkWComer

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laatsch55 said:
Wish I'd have known, I could have sent a bunch of those too....
Click to expand...
It's okay- NavLinear is cutting me a deal on them. Mouser backordered some caps that won't be in until Feb, so I'm gonna cop them from him as well.
The box came today (Wed)- thanks!

Screen Shot 2016-11-02 at 3.35.32 PM.jpg
 
laatsch55

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I mailed it on Monday and it got there Wednesday????????????????? Did UPS take over the USPS???
 
NavLinear

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laatsch55 said:
I mailed it on Monday and it got there Wednesday????????????????? Did UPS take over the USPS???
Click to expand...
USPS Flat Rate packages take two to three days typically. They've really picked up the delivery process for some package types. I've seen them on Sundays delivering packages - go figure.
 
roccus

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This is the time of year they bring extra help in for the holiday rush some areas will deliver on sundays not my town though they now dont even deliver if we have an inch of snow...
 
MarkWComer

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Shits 'n' giggles time...

Nothing to do today, so I decided to cut the can off of one of those fused transistors:



Closer inspection showed this. Clearly abnormal!



(Top lead is base, bottom lead is collector)
 
Last edited:
Gepetto

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MarkWComer said:
Nothing to do today, so I decided to cut the can off of one of those fused transistors:



Closer inspection showed this. Clearly abnormal!



(Top lead is base, bottom lead is collector)
Click to expand...

I think if you are careful, you can fix it :)
 
MarkWComer

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Complete...

DC offset: L: -.013v, R: -.012v. Bias at ~.36v this time, first time set to .35v. Rail voltages +/- 86v.

The DC protection circuit wasn't damaged, but a reliability question lurks in the back of my mind.

Usually when something fries in my house it's either eaten or sent to the recycle bin. Thanks to everyone for their help, input, jokes, and mailing stuff to me.

Lee: I didn't use the IC or the transistors for the DCP circuit- I'll mail them back to you.

Yes, Becky sings again!
 
laatsch55

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Ya better keep em Mark, ain't no biggie, glad to see she up and running!!! 86 eh?? She's a hottie!!
 
laatsch55

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MarkWComer said:
Nothing to do today, so I decided to cut the can off of one of those fused transistors:



Closer inspection showed this. Clearly abnormal!



(Top lead is base, bottom lead is collector)
Click to expand...

I really hope the bottom lead is the emitter..........I know, I KNOW.......picky sumbitch....
 
MarkWComer

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Umm... strange. It seems that I achieved a stable electric circuit, but not a usable electronic circuit. I announced that Becky sings again, but there's a polyp on her left vocal cord. I get a strange sound that sounds like a warbling reverb in the left channel that takes a ~second to decay when audio signal is applied. The spirit within me says to swap out ALL the output transistors regardless of whether I checked them as good or not, and the whole hFE test is just incomprehensible to me- can't make head or tail of the result (and my transistor test rig is "Mickey Mouse" at best).

Right channel is fine...

Three of the PNPs were fused, so I bought five, one of the NPNs was fused so I bought three. This leaves me short one NPN for complete swapout (ordering today...). I purposely bought more parts than I needed- a good/bad habit- and still ended short!

NOTHING can be easy, can it?
 
MarkWComer

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If video embed doesn't work: https://youtu.be/LaiFHTI0qYY. Watch it quick before WEA puts a copyright slap on the video and mutes all the sound!

(OOPS! They slapped me for "Aqualung")

Ruled out the preamp and speaker drivers. This sucker is kicking my ass. It must be the driver board, something else is wrong but it doesn't distort until I turn the volume up a bit. I have no idea where on the driver board to check and don't have a great assortment of test equipment to make a thorough assessment.

Relegated to the back burner until after New Years. I might just buy the Rev. E board after all...

<iframe src="https://www.youtube.com/embed/LaiFHTI0qYY" allowfullscreen="" width="560" height="315" frameborder="0"></iframe>
 
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laatsch55

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Pull one end of D9 or D10 on the affected channel and see if it stops then...that eliminates the protection circuit....
 
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MarkWComer said:
If video embed doesn't work: https://youtu.be/LaiFHTI0qYY. Watch it quick before WEA puts a copyright slap on the video and mutes all the sound!

(OOPS! They slapped me for "Aqualung")

Ruled out the preamp and speaker drivers. This sucker is kicking my ass. It must be the driver board, something else is wrong but it doesn't distort until I turn the volume up a bit. I have no idea where on the driver board to check and don't have a great assortment of test equipment to make a thorough assessment.

Relegated to the back burner until after New Years. I might just buy the Rev. E board after all...

<iframe width="560" height="315" src="https://www.youtube.com/embed/LaiFHTI0qYY" frameborder="0" allowfullscreen=""></iframe>
Click to expand...
Disable the SOA protection circuit first. Lift one end of D9 and D10 on each channel.
 
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